Plasma display panel having dielectric layer with specific color additive

ABSTRACT

A plasma display panel is able to contrast thereof by increasing a color temperature of the plasma display panel, which comprises a dielectric layer controlling a light transmittance for visible light of a certain wavelength emitted from a phosphor in the plasma display panel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of prior U.S. patentapplication Ser. No. 11/657,068 filed Jan. 24, 2007, which is aContinuation of U.S. patent application Ser. No. 10/242,757 filed Sep.13, 2002 now U.S. Pat. No. 7,253,559, both claiming priority under 35U.S.C. §119 to Korean Application No 75965/2001 filed on Dec. 3, 2001,whose entire disclosures are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma display panel, andparticularly, to a plasma display panel which is able to improve colortemperature thereof.

2. Description of the Background Art

Generally, a plasma display panel is a display device exciting afluorescent layer using ultraviolet rays of plasma and displaying animage using visible lights generated from the fluorescent layer.

Important properties the plasma display panel should have are high colortemperature more than 9300° K. and high contrast ratio. Herein, thecontrast means a ratio of brightness on the brightest part and on thedarkest part of a screen. The contrast is lowered by near infrared rayor visible light generated from discharge gas inside the plasma displaypanel or by outer visible light irradiated and reflected from outerside. Therefore, various methods are used for improving the colortemperature and the contrast conventionally. Hereinafter, a structure ofthe conventional plasma display panel will be described with referenceto FIG. 1.

FIG. 1 is a cross-sectional view showing a structure of plasma displaypanel according to the conventional art.

As shown therein, the conventional plasma display panel comprises: alower insulating layer 9 formed on a lower glass substrate 10; anaddress electrode 11 formed on a predetermined part of the lowerinsulating layer 9; a lower dielectric layer 8 formed on the addresselectrode 11 and on the lower insulating layer 9; a barrier rib 7defined on a predetermined part on the lower dielectric layer 8 fordividing each discharge cell; a black matrix layer 12 formed on thebarrier rib 7; a fluorescent layer 13 formed to have a predeterminedthickness on side surfaces of the black matrix layer 12 and of thebarrier rib 7 and on the lower dielectric layer 8 for emitting visiblelights of red, green, and blue colors by being supplied the ultravioletray; an upper glass substrate 2; a sustain electrode 3 formed on apredetermined part of the upper glass substrate 2 so as to cross theaddress electrode 11 vertically; a bus electrode 5 formed on apredetermined part of the sustain electrode 3; an upper dielectric layer4 formed on the bus electrode 5, the sustain electrode, and on the upperglass substrate 2; a passivation layer formed on the upper dielectriclayer 4 for protecting the upper dielectric layer 4. Hereinafter,operations of the conventional plasma display panel will be described.

As the upper glass substrate 2 and as the lower glass substrate 10 ofthe conventional plasma display panel, a soda-lime silicate (SLS) glasssubstrate is used. The lower insulating layer 9 is located on the lowerglass substrate 10, that is, the SLS glass substrate, and the addresselectrode 11 is located on a predetermined part on the lower insulatinglayer 9.

The lower dielectric layer 8 located on the address electrode 11 and onthe lower insulating layer 9 blocks the visible light emitted toward thelower glass substrate 10 direction. Also, a dielectric layer having highreflectance is used as the lower dielectric layer 8 in order to increasea luminous efficiency.

The fluorescent layer 13 consists of red, green, blue color phosphors,and emits visible light having a certain wavelength according tointensity of ultraviolet ray by the plasma which is generated on an areabetween the barrier ribs 7.

On the other hand, the sustain electrode 3 which crosses with theaddress electrode 11 is located on lower part of the upper glasssubstrate 2, that is, the SLS glass substrate, the bus electrode 5 islocated on a predetermined part of the sustain electrode 3, and thedielectric layer 4 having superior light transmittance is located on thebus electrode 5. Also, the passivation layer 6 is located on thedielectric layer 4 in order to prevent the dielectric layer from beingdamaged by the plasma.

After that, when voltage is applied to the sustain electrode 3, avoltage difference is generated between the bus electrode 5 and theaddress electrode 11 which crosses with the bus electrode 5 in verticaldirection. The gas located in an area between the barrier ribs 7 becomesplasma status due to the voltage difference, and therefore, the visiblelight of a certain wavelength is emitted from the fluorescent layer 13by the ultraviolet ray generated from the plasma. For example, in theplasma display panel, the discharge gas in a pixel area defined by thebarrier rib 7 becomes plasma status by a potential difference betweenthe address electrode 11 and the bus electrode 5. At that time, thefluorescent layer 13 is excited by the ultraviolet ray of the plasma toemit the visible light, and the plasma display panel displays an imageusing the visible light. That is, the plasma display panel excites thefluorescent layer 13 using the ultraviolet ray generated by Xe gas amongthe discharge gases such as He gas, Xe gas, and Ne gas which areinjected into a discharge space divided by the barrier rib 7, anddisplays desired color. At that time, it is required that the plasmadisplay panel should have high contrast. That is, the displayingproperty (that is, the contrast) is improved as the difference betweenthe highest brightness and the lowest brightness becomes larger.

Therefore, in order to improve the contrast of the plasma display panel,a material having superior light transmittance should be used. In orderto improve the light transmittance, MgO is used as a material of thepassivation layer 6, dielectrics of PbO-B₂O₃-SiO₂ group is used as amaterial of the upper dielectric layer 4 and of the lower dielectriclayer 8.

On the other hand, one of important features the plasma display panelshould have is high color temperature. For example, when a signal ofwhite color having no color signal is inputted (that is, R, G, and Bsignals are all inputted) into a display device such as a monitor and atelevision, the displayed white color is important for color designingin the display. Generally, the monitor uses color temperature of 9500°K., and the television uses the color temperature of 12000˜13500° K.

Generally, the television displays the white color as a light blue colorgroup to make viewers recognize the white color more clearly, and aprojection television uses white color of 6500˜7000° K. by the propertyof a lamp used as a light source and by the efficiency of the system.That is, the color temperature is controlled by controlling whitebalance, and the color temperature is determined by a luminance and achromaticity of base color. That is, ratio of R, G, B and colorcoordinate are determined by the luminance and the chromaticity of thebase color, and accordingly, the color temperature is also determined.

The fluorescent layer 13 in the conventional plasma display panel emitsvisible lights of green, red, and blue colors by vacuum ultraviolet rayshaving 147 nm wavelength. At that time, an emission intensity of greencolor is the largest among those visible lights, the emission intensityof the red color is the next, and the emission intensity of the bluecolor which affects to the color temperature most is the lowest.Therefore, since the emission intensity of the blue color is low in theconventional plasma display panel, the light properties (colortemperature) can not help being lowered unless the material of phosphor(fluorescent layer) is improved.

In order to increase the color temperature, the conventional plasmadisplay panel forms the barrier ribs 7 as an asymmetric structure toenlarge emission area of the blue phosphor more than those of the greenand red phosphors, and thereby the emission intensity of the blue colorvisible light is increased relatively more than those of the green andred color visible lights. However, although the above method is able toimprove the color temperature and the contrast, item difficulty infabricating processes is increased and an yield is also lowered.

Also, in another conventional plasma display panel for improving thecolor temperature, an electric signal which is inputted into a certainpixel is reduced in order to emit the blue color visible light than anyother visible lights. However, in this case, the luminance and thecontrast are lowered.

On the other hand, other conventional plasma display panel andfabrication method thereof is described in detail in U.S. Pat. No.5,838,106 registered on Nov. 17, 1998, U.S. Pat. No. 6,242,859registered on Jun. 5, 2001, and in U.S. Pat. No. 6,344,080 registered onFeb. 5, 2002.

As described above, the conventional plasma display panel forms thebarrier ribs asymmetrically to enlarge the emission area of the bluecolor phosphor in order to improve the color temperature by emitting theblue color visible light more than the red and green color visiblelights. Thereby, the item difficulty is increased in the fabricatingprocesses, and accordingly, the yield is decreased.

Also, the conventional plasma display panel reduces the electric signalwhich is inputted into a certain pixel in order to improve the colortemperature by emitting the blue color visible light more than the redand green visible lights, and thereby the luminance and the contrast arereduced.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a plasmadisplay panel which is able to improve a contrast thereof easily byincreasing a color temperature of the plasma display panel.

To achieve the object of the present invention, as embodied and broadlydescribed herein, there is provided a plasma display panel comprising adielectric layer for controlling a light transmittance of a visiblelight of certain wavelength emitted from a phosphor in the plasmadisplay panel.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a cross-sectional view showing a structure of a plasma displaypanel according to the conventional art;

FIG. 2 is a cross-sectional view showing a structure of a plasma displaypanel according to the present invention;

FIG. 3 is a table showing weight % of an upper dielectric layer of theplasma display panel according to another embodiment of the presentinvention;

FIG. 4 is a flow chart showing fabricating processes of the upperdielectric layer using a paste printing method; and

FIG. 5 is a flow chart showing fabricating processes of the dielectriclayer using a laminating method.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Hereinafter, the preferred embodiment of a plasma display panelaccording to the present invention which is able to improve a contrastand a color temperature thereof using a dielectric layer controlling alight transmittance for visible light of certain wavelength which isemitted from a fluorescent layer in the plasma display panel will bedescribed with reference to FIGS. 2 through 5.

FIG. 2 is a cross-sectional view showing a structure of the plasmadisplay panel according to the present invention.

As shown therein, the plasma display panel comprises: a lower insulatinglayer 9 formed on a lower glass substrate 10; an address electrode 11formed on a predetermined portion of the lower insulating layer 9; alower dielectric layer 8 formed on the address electrode 11 and on thelower insulating layer 9; a barrier rib 7 defined on a predeterminedportion on the lower dielectric layer 8 for dividing each dischargingcell; a black matrix layer 12 formed on the barrier rib 7; a fluorescentlayer 13 formed on side surfaces of the black matrix layer 12 and of thebarrier rib 7 and on the lower dielectric layer 8 for emitting red,green, and blue color visible lights by being supplied ultraviolet ray;an upper glass substrate 2; a sustain electrode 3 formed on apredetermined portion of the upper glass substrate 2 so as to cross withthe address electrode 11 vertically; a bus electrode 5 formed on apredetermined portion of the sustain electrode 3; an upper dielectriclayer 100 formed on the bus electrode 5, on the sustain electrode 3, andon the upper glass substrate 2 for increasing a transmittance of bluecolor visible light among visible lights of blue, red, and green colorsemitted from the fluorescent layer 13 more than those of the red andgreen color visible lights; and a passivation layer 6 formed on theupper dielectric layer for protecting the upper dielectric layer 6.

The upper dielectric layer 100 according to the present inventionincreases the light transmittance of the blue color visible light morethan the red and green color visible lights to improve the colortemperature and the contrast of the plasma display panel, and thereby,an image quality of the plasma display panel can be enhanced.

Hereinafter, structures except the upper dielectric layer 100 are sameas those of the conventional art, and therefore, explanations for thosewill be emitted. Therefore, the preferred embodiment of the upperdielectric layer 100 which is formed on the bus electrode 5, on thesustain electrode 3, and on the upper glass substrate 2 for increasingthe light transmittance of the blue color visible light more than thered and green color visible lights will be described in more detail.

The upper dielectric layer 100 of the plasma display panel according tothe present invention includes composition which is able to change thetransmittance for a visible light of a certain wavelength. That is, theupper dielectric layer of the general plasma display panel (referencenumeral 4 in FIG. 1) consists of dielectrics of PbO—B₂O₃—SiO₂ group, andtransmits visible lights of certain wavelengths (red, green, and bluecolor visible lights) as same transmittances. That is, the conventionalupper dielectric layer (reference numeral 4 in FIG. 1) shows sametransmittances for the red, green, and blue color visible lights, andtherefore, the red, green, and blue color visible lights emitted fromthe fluorescent layer 13 are transmitted through the conventional upperdielectric layer (reference numeral 4 in FIG. 1) as they are. Therefore,difference of the color temperature is determined by the properties ofthe conventional fluorescent layer 13.

On the contrary, the upper dielectric layer 100 according to the presentinvention consists of dielectrics of PbO—B₂O₃—SiO₂ group, oxide oftransition metal, and oxide of rare-earth element as mixing them, andthe transmittances for the red, green, and blue color visible lights canbe set to be different from each other. That is, the light transmittanceof the blue color visible light which affects to the color temperaturemost is set to be higher than those of the red and green color visiblelights, and therefore, quantity of blue color visible light representedon the front of the upper glass substrate 2 is relatively larger thanthose of the red and green color visible lights.

The upper dielectric layer 100 is able to filter the visible lightssince the upper dielectric layer 100 is colored. That is, the quantityof the visible light of desired wavelength (blue color visible light)which is transmitted through the colored upper dielectric layer 100 islarger than those of the other visible lights (red and green colorvisible light). For example, the upper dielectric layer 100 is coloredto be a certain color, and increases the visible light (blue colorvisible light) having the same wavelength as that of the colored colormore than the light transmittances of the visible lights (red and greencolor visible lights) having different wavelengths.

Composition of the upper dielectric layer 100 which is able to transmitthe quantity of the blue color visible light more than those of the redand green color visible lights comprises the dielectric of thePbO—B₂O₃—SiO₂ group, and one fillet or more among Nd₂O₃, CoO, and Co₃O₄.For example, as in following Table 1, the composition of the upperdielectric layer 100 may consist of dielectric of 55 weight %˜72 weight% PbO, 4.2 weight %˜20 weight % B₂O₃, 1 weight %˜21 weight % SiO₂ group;and a filler of 5 weight %˜23 weight % Nd₂O₃, 0 weight %˜3 weight % CoO,and 0 weight %˜3 weight % Co₃O₄. TABLE 1 Composition of the upperdielectric layer of PbO—B₂O₃—SiO₂—Nd₂O₃— CoO—Co₃O₄ group Component PbOB₂O₃ SiO₂ Nd₂O₃ CoO Co₃O₄ Weight % 55-72 4.2-20 1-21 5-23 0-3 0-3

Composition rate of the upper dielectric layer is given assuming theweight of the upper dielectric layer to be 100 weight percent. Herein,if the Nd₂O₃ is added in the upper dielectric layer 100 to be less than5 weight %, the light filtering effect is reduced, and if the Nd₂O₃ isadded more than 23 weight %, a transition point is too high. Also, ifthe CoO and Co₃O₄ are added more than 3 weight % in the upper dielectriclayer 100, the upper dielectric layer is colored excessively. That is,if the CoO and Co₃O₄ are added in the upper dielectric layer 100 morethan 3 weight %, the light transmittance of the plasma display panel isdeclined greatly, the color of outer appearance becomes too deep, andthe color is not balanced, and therefore, the upper dielectric layer 100can not be used.

FIG. 3 is a table showing composition of the upper dielectric layer 100according to another embodiment of the plasma display panel. That is,FIG. 3 is showing compositions of the upper dielectric layers 100according to 6 embodiments.

As shown therein, the upper dielectric layer 100 comprises 55 weight%˜72 weight % PbO, 1 weight %˜21 weight % SiO₂, 4.2 weight %˜20 weight %B₂O₃, 1˜7 weight % Al₂O₃, 0˜0.5 weight % MgO, 0˜0.5 weight % CaO, 0˜9weight % ZnO as mixing them. Also, the upper dielectric layer is formedby further being mixed with a filler consists of 0˜3 weight % CoO, 0˜3weight % Co₃O₄, and 0˜23 weight % Nd₂O₃.

In the table of FIG. 3, thermal expansion coefficients and transitionpoints according to the respective embodiments of the upper dielectriclayer 100 are shown. In addition, the thermal expansion coefficient ofthe upper dielectric layer 100 ranges 70×1⁻⁷/° C. through 85×10⁻⁷/° C.,and the temperature of the transition point ranges 380° C. through 472°C.

On the other hand, the upper dielectric layer 100 may use fillers ofNiO, MnO, Mn₃O₄, Gd₂O₃, Cr₂O₃, V₂O₅, and CuO besides the filler ofNd₂O₃—CoO—Co₃O₄ group. The NiO, MnO, Mn₃O₄, Gd₂O₃, Cr₂O₃, V₂O₅, and CuOare materials which are able to color the upper dielectric layer 100,and one or more materials among those NiO, MnO, Mn₃O₄, Gd₂O₃, Cr₂O₃,V₂O₅, and CuO can be mixed to use.

On the other hand, the upper dielectric layer 100 is formed by using apaste print method or a laminating method. The methods will be describedin detail with reference to FIGS. 4 and 5.

FIG. 4 is a flow chart showing a method for fabricating the upperdielectric layer 100 using the paste print method. Hereinafter, themethod for fabricating the upper dielectric layer 100 will be describedin more detail in order.

1. Materials for fabricating the upper dielectric layer 100 are chosenwith reference to Table 1 or the table in FIG. 3. At that time,compositions are chosen according to the characteristic of the plasmadisplay panel which will be fabricated (S41).

2. The chosen materials are mixed together (S42).

3. The mixed material is put into a platinum crucible, and melted bybeing heated with 1000˜1400° C. temperature (S43).

4. The melted material is quickly frozen using a water quenching methodor a quenching roller (S44).

5. The frozen material is ground to fine powder (S45).

6. The fine powder and an organic solvent are mixed to make a paste(S46).

7. The fabricated paste is applied on the glass substrate 2 and dried toform a filter (dielectric layer 100) for filtering the visible lights(S47).

FIG. 5 is a flow chart showing a method for fabricating the dielectriclayer using the laminating method. Hereinafter, the method forfabricating the dielectric layer using the laminating method will bedescribed in detail in order.

1. Materials are made to fine powder through the mixing, melting, quickfreezing, and grinding processes as in the paste print method (S51˜S55).

2. The fine powder is mixed with an organic solvent, the mixed powder ismade as a slurry form having low viscosity, and the powder of slurryform is molded to be a dry film using a casting method (S56).

3. The dry film is coated on the upper glass substrate to form a filter(dielectric layer 100) for filtering the visible light. The passivationlayer 6 such as MgO may be formed on the dielectric layer 100 forprotecting the dielectric layer 100 (S57).

On the other hand, the filter for controlling the light transmittancefor the visible lights of certain wavelengths emitted from thefluorescent layer in the plasma display panel, that is, the upperdielectric layer 100 may be formed on the upper glass substrate 2.

As described above, the plasma display panel according to the presentinvention increases the transmittance of blue color visible light morethan those of the red and green color visible lights relatively throughthe upper dielectric layer 100 which is able to change the lighttransmittance for the visible light of certain wavelength, and thereby,the color temperature and the contrast of the plasma display panel canbe improved easily.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1. A plasma display panel comprising of: an upper glass substrate; asustain electrode formed on the upper glass substrate; a bus electrodeformed on the sustain electrode; an upper dielectric layer having acoloration additive that increases a transmittance of visible lighthaving a blue color wavelength emitted from the glass substrate of theplasma display panel to a higher degree than that of visible lighthaving red and green color wavelengths formed on the bus electrode, thesustain electrode and the upper glass substrate; a passivation layerformed on the upper dielectric layer; a lower glass substrate; anaddress electrode formed on the lower glass substrate; a lowerdielectric layer formed on the address electrode and the lower glasssubstrate; and a fluorescent layer formed on the lower insulating layer.wherein the upper dielectric layer consists essentially of PbO, SiO₂ andAl₂O₃, and the coloration additive comprises at least one of CoO, Co₃O₄or Nd₂O₃, and at least one of NiO, MnO, Mn₃O₄, Gd₂O₃, Cr₂O₃, V₂O₅ orCuO.
 2. A plasma display panel comprising of: an upper glass substrate;a sustain electrode formed on the upper glass substrate; a bus electrodeformed on the sustain electrode; an upper dielectric layer having acoloration additive that increases a transmittance of visible lighthaving a blue color wavelength emitted from the glass substrate of theplasma display panel to a higher degree than that of visible lighthaving red and green color wavelengths formed on the bus electrode, thesustain electrode and the upper glass substrate; a passivation layerformed on the upper dielectric layer; a lower glass substrate; anaddress electrode formed on the lower glass substrate; a lowerdielectric layer formed on the address electrode and the lower glasssubstrate; and a fluorescent layer formed on the lower insulating layer.wherein the upper dielectric layer consists essentially of SiO₂ andAl₂O₃, and the coloration additive comprises at least one of CoO, Co₃O₄or Nd₂O₃, and at least one of NiO, MnO, Mn₃O₄, Gd₂O₃, Cr₂O₃, V₂O₅ orCuO.
 3. The plasma display panel of claim 1, wherein the colorationadditive further comprises CoO, wherein the coloration additive consistsof 1 weight % of CoO.
 4. The plasma display panel of claim 1, whereinthe coloration additive includes Co₃O₄ which if less than 3 weight %. 5.The plasma display panel of claim 1, further comprising of: a lowerinsulating layer formed on the lower glass substrate.
 6. The plasmadisplay panel of claim 2, wherein the coloration additive furthercomprises CoO, wherein the coloration additive consists of 1 weight % ofCoO.
 7. The plasma display panel of claim 2, wherein the colorationadditive includes Co₃O₄ which if less than 3 weight %.
 8. The plasmadisplay panel of claim 2, further comprising of: a lower insulatinglayer formed on the lower glass substrate.